Due to the increasing dependence on fossil fuels to meet our energy needs during the last few decades, the release of the greenhouse gas CO2 has increased exponentially. Approximately 33 billion tons of carbon in the form of CO2 was emitted into the atmosphere in 2010, and this trend is increasing every year. Due to rapid development worldwide, the energy demand is increasing. Unfortunately, there will be no significant change in the coming years in terms of the source of this energy, and fossil fuel will remain the major source for fulfilling this energy requirement.
Therefore, there are extensive efforts underway to develop technologies that will allow fossil fuel to be used with reduced CO2 emissions. CO2 capture and sequestration using solid adsorbents have received extensive interest due to their good sorption capacity, stability, ease of handling and reusability. A wide range of materials, such as amine-functionalized silica, oxides, zeolites, carbon, polymers and, recently, metal organic frameworks (MOFs), have been used. Among these materials, organic amino-functionalized silica has shown promise in fulfilling the desired working capture capacity. Although functionalization with organic amino moieties such as (3-aminopropyl)triethoxysilane (APTES) can result in high amine loadings onto the support material, the longevity of this type of material appears to be limited due to leaching of the organics from the support. Other disadvantages include the structural degradation of the support upon grafting and a drastic decrease in textural properties (surface area, pore volume and pore size). Additionally, the grafting processes are not clean and green because they require the use of expensive chemicals (such as APTES) or toxic solvents (e.g., toluene) and require multistep operations (extractions, filtration, washing, and drying). More critically, their thermal stability is a major concern. Degradation of the amines from solid supports can reduce the capture capacity, restrict the regeneration and reusability and produce toxic volatile molecules. Therefore, there is a need to overcome these serious issues.